Incandescent electric lamp



1,635,320 July 1 1927- J. A. HEANY INGANDESCENT ELECTRIC LAMP Filed June28, 1918 ATTORNEY l inserting them in an opening in the glass 1,635,320PATENT- o Fics.

:oim min min. or raw mm. 0011113011001.

IROAIDISCBNT ELECTRIC LAMP.

\ Application fled June as, ms. was Io. mam.

This invention relates to improvements in incandescent lamps or likedevices having gas tight receptacles with leading in wires sealedgas-tight thr' ugh a vitreous wall.

In the manufactu of. incandescent lam s, the leading-in wires are sealedin y stem of the lam heating the lass until it is softened and t n sueezing e soft glass firmly into contact wit the wires, as by theapplication of a clamp. The glass remains in contact with the wiresuntil it setsito a hard condition from its soft or plastic state.

As the glass and wires are brought to normal temperatures, a contractionof the glass and wires takes place. If the seal thus made is nottight,'then a leakage will occur, which will cause a rapid deteriorationof the lamp, thus cutting short the life thereof.

Platinum has heretofore been used as a leading-in wire, because it wasendowed with certain characteristics which made its use successful undercertain conditions. Attempts have been made to make use of other metalsin place of platinum, but most of' those attempts have proved failures.Several reasons have been ascribedflfor these failures. The first reasongenerally advanced is that the coefiicients of expansion of the metaland lass difiered. From that it has been argue that the expansion of themetal has cracked, the glass and destro ed the seal. A further exlanation is that w en the metal is heated at t e time of the makin ofthe seal, an oxide of the metal is forme on the surface of the wire,which interposes ,a oroiis film between the Iinetal and the glass a1owing a leakage to ta place. The a pearance of bubb es in the glassaround t e wire, which undoubtedl prevents the seal from being ti ht, isattributed to two difierent causes. The first explanation of thephenomenon is that occluded ases of the metal have been driven outformin'g'these bubbles. A second explanation is that these bubbles arethe result of some chemical reaction between the metal and some elementof the glass.

My experiments have convinced me that the true cause of the failure ofthe seal is the-formation of the oxide of the metal. Unless there is avery considerable change in tem erature, the difierence in the expansion0 the glass and the metal is not suflicient to cause the glass to crack.Ifcare be taken in the arrangement of the elements of the lamp so thatthe and stem are not sub'ected to a high heat, there will not be a.

su cient difference in the ex ansion to cause a cracking to occur. Theam s of to-day are so constructed as to comp y with the aboverequirements, thus obviatin the possibility of a failure of the seal. usto the difierence in the coeflicien ts of expansion. Furthermore thefailure of the seal is not due to occluded gases. -When the leading-inwires are sealed into the stem the temperature s far .greater than atany subsequent time in the .life of the lamp. As a result whatever.occluded gases there may have are all driven out. The metal is preventedfrom absorbing any gas due to the fact that the glass is made tofiowalong the wires.

By way of experiment a copper lead wire I was placed in a glass tube,one end of which was sealed. The other end was attached to a vacuum lineand the tube was exhausted. Beginning at the sealed end and-working inthe direction of the exhaust, the tube was heated until plastic andforced into contact with the wire. In this way any occluded gasespresent were driven off and carried away and the formation of an oxidewas prevented. The wire, after the o eration, was bright showing theabsence of tlie oxide. But, nevertheless, the bubbles were resent. Thisexperiment shows that the bubb es were not due to occluded gas or theformation of an made, but rather are due to some chemical reactionbetweenthe metal and the glass.

The reason why platinum wire was so successful as a leadingrin wire wasnot because of the fact-that its coeflicient of expansion is nearly thesame as that of glass, but rather because it is non-oxidizable and doesnot react chemically with the lass. Its disadvantages, however, arenearfy as great as its advantages. In the first place it is quitea'pooi" conductor of electricity, secondly its cost makes itnearlyprohibitive and thirdly it is almost impossible to obtain any atthe pres ent time. a

It is one of the objects ofiny invention to provide a wire which can beused as leadingin wires and which will make a perfect seal with theglass stem.

A further object is to provide a wire which can be extended from thestem into the body of-the bulb and act as the anchor wires to supportthe light emitting portion of the lamp.

To accomplish these objects, I make use of a lead alloy wire, a leadcoated wire or just a plain lead wire. When any of these wires are madeuse of, the wire, after the sealing has been accomplished, is bright mcolor showing that thereis no oxide remaining thereon after the processof sealin -in is completed. This phenomenon is explained as follows: Thetype of glass which is ordinarily used in the formation of the stem ofan incandescent lamp is that known as lead glass. When this glass is ina plastic condition it has a greatafiinit for lead oxide. The lead oxideformed in t e process is completely absorbed by the glass. It is notknown exactly what occurs wlth respect to the other metal used in thealloy wire. There may be no oxide of this metal formed or the oxide ofthis metal, if formed, is masked by the lead oxide. The fact remains,however, that themetal has no oxide coating and the seal is perfect.Furthermore, there are no bubbles formed in the glass surrounding thewires. Whatever chemical reaction takes place is of such a nature thatno detrimental effect is had upon the seal.

The accompanying drawing discloses, in the single figure thereof, anordinary incandescent electric lamp, the vseal of which is formed inaccordance with my invention.

In the drawings, 1 is the bulb, 2 the stem, 3 the illuminant, 4 theleading-in wires, and 5 the sealing-in wires.

\Vhen either the lead alloy wire or the lead coated wire is used thewires to form the leading-in wires are placed in the glass stem 2 in theusual way, heated and the glass pressed around the wires 4 in the wellknown manner. The lead will not melt out of the alloy nor will it runoil? from the wire if it be properly coated thereon. It will soften whensubjected to the heat required to melt the glass forming the stem butwill remain in place. When a plain lead wire is used, it is necessary toprovide a construction so that the lead will not flow away upon cominginto a molten condition.

The alloy wire may have as its constituents any one of a number ofmetals, such as copper, iron, aluminum, nickel and the like; the onlyabsolute rqeuirement is that one of the constituents shall be lead. Thewire which is coated with lead may be anyone of the above. The onlyrequirement of these metals is that they shall not have a volatil- Inthe case of the alloy wire, the leading in wires may be extended intothe body of the bulb 1 to act as supports for the light emitting portion3 of the lamp. In such a case it is contemplated that some other metalbe incorporated in the wire to give it a certain amount of resiliency sothat it will maintain the light emitting portion of the lamp in properposition.

The method above outlined results in overcoming the difficultiesheretofore experienced in the forming of a seal for incandescent lamps.It contemplates no change in the composition of the glass now used forstems and bulbs. The resulting seal is perfect inasmuch as the oxidesformed on the wire are absorbed by the glass leaving a clear surface ofmetal which makes a gas tight contact with the glass. Furthermore, thereare no resulting bubbles to allow a leakage through the stem 2. There isno cracking of the stem as the difference in expansion between the metaland glass is inconsiderable due to the fact that the temperature of thelamp is not sufiiciently hi h to cause appreciable expansion. Also, t ewire thus used is quite inexpensive and easy to obtain.

I claim as my invention:

In an incandescent electric lamp, the combination of a stem formed oflead-glass, a filament in said lamp and leading-in wires formed of acopper-lead alloy positioned in the stem and connected to said filament,the lead forming from five to ten per cent of the alloy.

In testimony whereof I hereunto atfix my signature.

JOHN ALLEN HEANY.

